Airwaves: Bringing an old vintage radio back to life

Way back in October of 2011, I wrote of a five-tube AM radio I received from the estate of the parents of my friend, Dean. It is a model 56B manufactured around 1947 in Los Angeles by the Gilfillan Brothers. At the time I had not done anything with it because I know that simply plugging in and turning on ("energizing," as my electronics shop teacher Mr. Reese used to insist) a radio can lead to the untimely demise of many old electronics. If something inside shorts out and it lets out smoke, the item no longer works. But I digress.

With the help of Long Beach reader Craig During, who set me up with a Variac, I was able to slowly bring the old radio -- which I am sure had not experienced electricity since the 1960s -- back to life. The Variac -- a brand name for a variable autotransformer -- allows you to start low and increase the voltage supplied to old electronics so that the old parts, particularly capacitors, don't explode or release smoke from the sudden rush of 120 volts of power.

But there was a problem. As with many old radios, it exhibited a hum. A loud hum. Which meant a bad part or two, most likely a filter capacitor in the power supply. I set the radio aside.

Well last week I finally did something with it. I headed over to Torrance Electronics and bought replacements for all the old wax and paper capacitors, as well as two electrolytics that substituted for an old canister capacitor -- the most likely source of the loud hum -- that is no longer available.

The young salesman at the store was quite helpful, even if he had never seen an AM radio chassis before. "Is that a timer?" he asked of the dial. That made me realize that it has probably been years since radios with actual dials for tuning have been readily available.

A short time later, after some cutting and soldering, I was ready for the big test.

It passed.

Gone is the hum, in are the sounds of what passes these days for AM radio entertainment. Not the most selective radio I have ever used, but probably typical for a fairly generic design five-tube AM radio.

Perhaps the most interesting part of the repair had to do with the fact that, although the 56B was not manufactured very long, the schematic for mine printed on the chassis did not match the design of the chassis itself. There were numerous parts substitutions or design changes, including fewer capacitors overall and a main filter capacitor that had only two sections instead of three as was called for on the schematic parts list. I also found that my radio used smaller and different numbered tubes than was shown on another model 56B being rebuilt by someone on the Internet.

And to show you how far we've progressed, I was, um, let's just say "reminded" about a design "feature" carried by just about every similar radio of its time: You are directly exposed to 120 volts when you touch the chassis (or exposed screws or knobs) when the radio is on, or off, depending on which way the power cord is plugged in. This is because one wire of the power cord is tied directly to the chassis. I was shocked into remembering -- literally.

The design came as a cheap way to avoid using expensive (at the time) power transformers; the tubes were wired in series so that the voltage needed matched the voltage of the house. Safety came only from the insulating knobs and the knowledge not to touch anything metal under the radio. Back then it was just accepted; imagine the lawsuits if such a radio were released today.

Overall I still like the design of my Delco from the same era (a gift from my father to my mother). But the fact that the Gilfillan was made right here in Southern California makes it a special find.

Richard Wagoner is a San Pedro freelance writer. Send questions to him by email to rwagoner@cox.net.